Some wells can be completed with sand control screens for controlling sand production. Other wells can additionally have a gravel pack placed around the screens to control sand production. Produced sand is undesirable for many reasons. The sand is abrasive to components within a well and must be removed from the produced hydrocarbon fluids at the surface.
For a complete gravel pack, it is often preferred to completely pack an annulus external to production tubing across a sand face or external to a sand screen without leaving any voids. Failure to obtain a complete gravel pack can result in lower productivity and/or sand-producing gravel pack. This incomplete packing is often associated with the formation of sand bridges in the interval to be packed. Sand bridges can prevent placement of sufficient sand along a screen on the opposite side of the bridge.
Different methods of gravel packing are available. One method can be referred to as using an alpha-beta technique or sand duning technique. In those methods, a sand concentration or sand slurry can be pumped into the well system. The sand slurry can exit a gravel pack port and build a dune or collection along a portion of a screen. As the fluid continues to flow past the dune at a certain velocity, the top of the dune is removed. The alpha wave, which progresses along the wellbore, includes gravel that can be deposited by gravity on the bottom side of the annulus around a screen, a blank pipe, a workstring, or other conduit.
The presence of gravel slurry flowing in the annulus combined with the force of gravity can often cause some gravel to fall and accumulate on the floor of the annulus for wells with horizontal deviations. The slurry flow velocity above the gravel dune can cause shear force sufficient to wash away higher accumulations of gravel. The shear forces of the slurry fluid flow can cause the gravel accumulation to reach a equilibrium gravel dune height in the annulus. The duning process can continue as the slurry flow velocity in the annulus is sufficient to cause enough shear force to prevent gravel accumulation. Once axial slurry flow is reduced to a level that is inadequate to shear away gravel at the top of a dune, the slurry flow along the annulus can be blocked. At such blocking, the alpha wave gravel placement can be terminated. Fluid exiting the annulus prior to the end of the screen may prevent the alpha wave from progressing uniformly to the end of the screen. The beta wave then fills up the downstream portion of the well as the sand moves its way upstream as it piles up along the length of the well. Uniform beta packing often occurs when the fluid can flow into the screen in a uniform manner along its length. However, in some well systems, the alpha wave may not reach an end of the wellbore, thus stalling at an intermediate portion of the wellbore due to a number of factors, such as the loss of fluid velocity or fluid lost to the formation. The result may be an incomplete pack.
An alternate approach can include replacing the use of a beta wave gravel deposition by adding additional gravel deposit height in the annulus using one or more successive alpha wave deposit phases of gravel packing. Gravel placement with alpha wave deposition can be uniform and continuous up to the point where gravel slurry carrier fluid flow velocity exterior to the screen is sufficient to transport gravel along the length of the screen. Conditions that can preclude uniform and continuous gravel placement by alpha wave deposition include irregularities in the wellbore diameter or excessive hole rugousity, excessively high or inconsistent gravel concentration per unit volume of slurry, and slurry flow velocities which are either too high or too low.
Some well systems can be gravel packed using alternate-path gravel packing. In some well systems, the alternate-path gravel packing can use shunt tubes or other bypass flow paths to provide a complete gravel pack.
In a well designed conventional gravel pack screen and tool assembly, the fluid flow paths and cross sectional areas may be arranged such that in some cases, a substantially complete gravel packing using both alpha wave and beta wave or multiple alpha wave gravel placement may be obtained. However, difficulty in the art has arisen when gravel packing wellbores employing screens with flow management devices. Some such well bores and/or completions can employ flow restricting devices, such as an inflow control device, an autonomous valve, or screens that have means of controlling fluid inflow at isolated points along the screen. The introduction of such inflow control devices can provide difficulties in obtaining a complete gravel pack about a screen of the well system. Such isolated points of fluid ingress through a screen may prevent uniform packing during the beta wave gravel depositing phase of the alpha wave and beta wave packing process.
In some well systems, the inflow control device may impair or prevent a successful placement of the gravel pack around the screen when using these conventional slurry pumping techniques. In some cases, the inflow control device can restrict the available flow rate through the screen during the gravel packing operation. As a result, few (if any) wells have been completed having an integral flow control device with a complete and uniform gravel pack installed about the screen.
Therefore, assemblies and systems are desirable that can provide an open hole gravel pack in well completions having a flow restricting device and screen, particularly in horizontal well completions.